A,B不相对 AB A,B are two spaces apart(A,B相隔为2) (A□B) or |A-B|=2) y3 L% y* k% V; ~
* Two spaces separate A and B = A,B are two spaces apart
E* Q7 Y6 q5 |& w# j 又如:A is two floors above B, 则A和B只有一层相隔
3 S) d4 ?4 P7 K0 h) g4 d4 i8 j 又如:A is two days before B, 则A与B之间只有一天之隔
0 |; }; W6 [& a 区别:A,B之间有两个元素 (A□□B)
* P. q( j9 \# N A is to the right of B: B-A
% o8 @$ w: ~5 D: u: L A is to the immediate right of B: AB u$ ]; B7 u$ U W8 d, a6 K8 Q
B is to the right of either A or C, but not both: (A-B-C) or A/C——B——A/C
! i0 B* ], Q6 J: @. t 区别:B is between A and C: A-B-C+ x* Y1 _4 n8 D" b" T
区别:B is immediately between A and C: (ABC)
; q4 Q. ?% Z G =B is (immediately) next to both A and C.
6 Y$ N1 u8 S8 v5 v7 @ If A is next to B, it is not next to C: ~(BAC): ?! [' i! F" G3 P& E* b' G
2.表选择" f" a) j! J) M' |4 f$ b* V
If A, then B(A入选则B入选) A→B 逆反命题 -B→~A* N) D3 Q6 v D( n4 {" T7 v* `
选A则不选B A→~B (但可同时不选); s; U- a, j. m! m6 c. j" F, ]
=A,B不全选 A→~B 逆反命题 B→~A(区别A,B全不选)
$ Z, U& O- ?9 L: V0 k 同理:A灯亮则B灯灭 A→~B 逆反命题 B→~A (但A,B可同时灭)' s. Z6 K4 O/ i) W8 t0 S+ x: ~; w
另外:A is off if and only if either B or C is on: B/C→~A (B和C可同时亮时A也不亮)0 a; {6 s! c: _' r3 J6 o8 @1 N
逆反命题 A→ ~B/C (A亮时,B,C都不能亮,即neither A nor B is on=both off)
. N9 A6 i1 }+ y. g9 G. T If A, then B, and if B, A: AB" C7 s5 d7 l$ f8 s- G
=If A, then B, and if ~A, ~B
0 Y, C$ w- J! q4 i4 \ =A if and only if B
5 z" p: b* e; u+ l' ? =B if and only if A
% m% t' o+ |# u6 T# ?" c! u =Neither A nor B unless the other is selected. p0 t& J+ o6 Z$ Y$ O: [/ c1 H% Z
A only if B: A→B 逆反命题 B→~A
- U7 m* }% Q8 Q# T- ` A unless B: ~A——>B 逆反命题 ~B→A
* k/ d- ]. R! W+ p6 s% Z, k; t 区别:Not A unless B: A→B 逆反命题 B→~A. [ o6 o# I0 ]
Only A works in the afternoons: only A=pm7 P% ?- a- B3 |7 `
区别:A only works in the afternoons: A=pm) A; k* v U; p; ?3 r* m
If A occurs in a word, it occurs an odd number of time: J→J=odd#
$ u$ m9 s% v n2 p2 I; F: y9 M Only As are Bs: B→A0 Q+ m0 ]7 R: O
=only if A, B
! V5 `: e2 N9 p j- _ No As are Bs. A≠B (A,B无交集) |